Project Abstract The long term goals of this project are to understand the origins of muscle weakness, atrophy, and associated changes in intrinsic mechanical properties of the paralyzed muscle after spinal cord injury (SCI), and to develop tailored, innovative treatment strategies based on these findings. We propose to apply a multifaceted electromyography (EMG) analysis to the same group of SCI subjects for improved understanding of complex neuromuscular changes after SCI. Such analysis takes advantages of various techniques, including high density surface EMG, single fiber EMG, concentric needle EMG, and compound muscle action potential (CMAP) scan, etc. These techniques offer a significant amount of complementary information about muscle and motor unit structure and function. The proposed combination of these techniques will help better differentiate or quantify complex neuromuscular factors underlying weakness and other associated changes after SCI, such as motor unit loss, motor unit control property alterations, muscle fiber atrophy, and denervation/ reinnervation changes. The findings will have important clinical value to diagnosis, examination and medication study of SCI, and provide guidance for the development of rehabilitation strategies and devices toward restoration of normal muscle function.